Improvement in devices for preventing backlash of machinery



J. A. HAl-NER.

Device for Preventing Back-Lash of Machinery.

PatenjedQct. 5,1875.

gm J jIJV'TOR WITNESSES Wm B Q. A M.

.dttorney WASHINGTON D C UNIT D STATES tlif .R OFF JOHN A. HAFNER, OF PITTSBURG, PENNSYLVANIA.

IMPROVEMENT IN DEVICES FOR PREVENTING BACKLASH 0F MACHINERY.

Specification forming part of Letters Patent No. 168,481, dated October 5, 1875; application filed May 31, 1875.

To all whom it may concern:

Be it known that 1, JOHN A. HAFNER, of Pittsburg, in the county of Allegheny and in the State of Pennsylvania, have invented certain new and useful Improvements in Device for Preventing Backlash of Machinery; and do hereby declare that the following is a full, clear, and exact description thereof, reference being had to the accompanying drawings and to the letters of reference marked thereon,

' making a part of this specification.

My invention relates to an improvement upon Letters Patent No. 86,533, granted to me February 2,1860; and it consists in forming the coils of the spring as therein patented to me of varying thicknesses, increasing in size from the inner to the outer one, for the purpose of equalizing the strain on the spring; and in enlarging the bottom part of the hub, to which this spring is connected, so that the greatest strength is had upon that part where the greatest strain is caused, all as more fully hereinafter set forth.

In order to enable'others skilled in the art to which my invention appertains to make and use the same, I will now proceed to describe its construction and operation, referring to the annexed drawing, in which Figure l is a plan view of myinvention, and

Fig. 2 is a section of the same.

My coil-spring is made of two or more plates,

A A, riveted together at their inner ends and bent to form a hook, a. It is well known in the construction of flat coil-springs that, the plates being of the same thickness, a spring of small coils will be of greater stiffness than one of larger coils, and hence, when a spring is made of two or more plates of the same thickness the strain upon the various plates is unequal, and the spring will not have the strength it ought to possess. To obviate this difficulty, I make the plates A A of varying thickness-that is, each plate is made thicker that the one immediately within it, and such increased thickness should be in proportion to the increase in the size of its coils, so that all the plates in the spring will be of equal stiffness. The outer plate of the spring is formed at its outer end with a loop, I), to be fastened to part of' the machinery to which it is to be applied. The hook or of the spring is inserted in a notch, .70, made in an eccentric flange, d, which is formed around the exterior of the hub B at or near the center thereof. This hub is made with an interior longitudinal groove or key-seat, "i, for the key to enter in fastening the hub to the shaft on which it is to be applied. The part B of the/hub above the flange d is made of reduced thickness, while the part B below said flange is made of increased thickness, giving it the requisite strength just where needed in driving the key,'while there is no superfluous metal at the other end, making the hub as light as possible.

The spring and hub may be used on any classes of machinery where applicable.

In some cases I may shrink a wrought-iron band around one end of the hub to make the same larger and of greater strength.

It will be understood that in my patented device hereinbefore referred to the plates of the spring were of the same thickness, and

that the hub was of the same size on each side of the central circular flange.

The improvement hereinbefore described is of such a nature in practice that the defects found in my former device are remedied.

I am aware that it is not new in carriagesprings to form the leaves of decreasing thicknesses and widths; hence I do not claim such, broadly, as my invention.

Having thus fully described my invention, what I claim as new, and desire to secure by Letters Patent, is-

The combination of the hub B, having central flange d and notch 00, and made larger at the bottom than at its top, with the spring A, made of a series of leaves of varying thicknesses, and having hook at and loop d, all substantially as and for the purposes set forth.

In testimony that I claim the foregoing I have hereunto set my hand this 26th day of May, 1875.

JNO. A. HAFNER.

Witnesses:

O. L. EVERT,

W. A. SKINKLE. 

